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The gestation time of humans has an approximate Normal distribution with a mean of 250 days and a standard deviatim- 6.0 days. A simple random sample of 
n newborns is to be taken.
What is the minimum sample sized needed so that the sampling distribution of 
bar(x) has a standard deviation of 0.5 day?
15
144
12
250

The gestation time of humans has an approximate Normal distribution with a mean of 250250 days and a standard deviatim- 66.00 days. A simple random sample of n n newborns is to be taken.\newlineWhat is the minimum sample sized needed so that the sampling distribution of xˉ \bar{x} has a standard deviation of 00.55 day?\newline1515\newline144144\newline1212\newline250250

Full solution

Q. The gestation time of humans has an approximate Normal distribution with a mean of 250250 days and a standard deviatim- 66.00 days. A simple random sample of n n newborns is to be taken.\newlineWhat is the minimum sample sized needed so that the sampling distribution of xˉ \bar{x} has a standard deviation of 00.55 day?\newline1515\newline144144\newline1212\newline250250
  1. Identify Formula: Step 11: Identify the formula to find the minimum sample size needed to achieve a specific standard deviation of the sample mean. The formula is n=(σdesired standard deviation)2 n = \left(\frac{\sigma}{\text{desired standard deviation}}\right)^2 where σ \sigma is the population standard deviation.
  2. Plug in Values: Step 22: Plug in the values into the formula. Here, σ=6.0 \sigma = 6.0 days (given as the standard deviation of the population), and the desired standard deviation of the sample mean is 00.55 day. So, n=(6.00.5)2 n = \left(\frac{6.0}{0.5}\right)^2 .
  3. Calculate Inside Parentheses: Step 33: Calculate the value inside the parentheses first. 6.00.5=12.0 \frac{6.0}{0.5} = 12.0 .
  4. Square Result: Step 44: Now, square the result from Step 33 to find n n . 12.02=144 12.0^2 = 144 .

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